Audible signal devices are used across a broad range of mechanical and electromechanical devices. A typical audible signal device consists of a selectively activated speaker or other sound-generating device coupled with an electrical power system. Familiar examples of audible signal devices include any of the various beepers, buzzers and bells activated in a work machine when a particular operating condition is detected. For instance, in many work machines a bell is activated within earshot of an operator to alert him or her to a particular engine condition, such as low oil or elevated engine temperature.
Work machine audible signal devices have evolved significantly over many decades of technological development. With the advent of electronic control over many aspects of work machine operation, audible signal devices are now often operably coupled with an electronic control module of the work machine. One or more sensors are provided, also coupled with the electronic control module, for monitoring various aspects of operation, such as engine temperature, oil pressure, fuel pressure and level, and even tire pressure. When out-of-specification conditions are detected by the electronic control module from any of the sensors, the electronic control module may activate the audible signal device to alert the operator, allowing him or her time to shut down or adjust the work machine prior to the occurrence of any damage or other undesirable condition.
Several audible signal device designs are known in the art. The oldest of these are conventional “buzzers,” also known in the art as electromechanical and electromechanical-based audible signal devices. These devices generally include an electromagnet that actuates an armature plate to strike a diaphragm. The output frequency of such devices is generally in an acceptable audio range, around 500 Hz, and is therefore not overly directional, nor too high for some operators to hear, as may be the case with higher frequency devices.
Nevertheless, component wear and environmental degradation over time are problems inherent in any design having moving parts that strike one another. Where electrical contacts directly connect with the movable armature, as in an electromechanical-based design, the contacts will also wear over time, and may be susceptible to moisture-related corrosion. Moreover, overheating during continuous operation is a known problem with existing electromechanical-based designs, as is excessive radio frequency output, which can interfere with the work machine electronics and reduce operating efficiency.
In more recent years, piezoelectric based designs have become commonplace. A piezoelectric based design typically utilizes a ceramic plate having piezoelectric crystals therein that change conformation as a voltage across the same is adjusted. As a result, the crystals can induce a vibration, and hence sound, in a diaphragm as they rapidly change conformation in an oscillating electric field. While such devices have been successful in certain applications, they are characterized by a relatively high frequency sound output, about 2100 Hz and above, which may be difficult to hear for some operators having reduced hearing sensitivity to higher frequencies. Further, the high frequency sound can create regions of varying loudness as it reflects off surfaces in the work machine operator cab. Because work machines often operate in relatively loud work environments, such as construction zones, mines, and lumber mills, it can be challenging for operators to detect an audible signal quickly and positively, such that they are able to shut down or adjust the machine operation without undue delay.
In spite of a number of shortcomings, the above audible signal device designs have each proven useful in various applications over the years. However, where one design may be well suited to a first type of work machine, it may be less well suited to a second type where the work machines have electrical systems with differing operating voltages. For example, a relatively small track-type tractor will typically have a different operating voltage for its electrical system than a relatively large work machine such as a motor grader. Despite this, both work machines require various monitoring devices and signal means, such as audible signal devices, which need not necessarily be significantly different in design. In the past, engineers typically developed a particular audible signal device suitable for use in a particular line of work machines, rather than utilizing audible signal devices applicable commonly to dissimilar work machines.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.